Heat exchanger with improved fins

ABSTRACT

The invention relates to a heat exchanger ( 1 ) comprising at least one tube ( 2 ) for heat transfer fluid to flow through, connected to at least one heat dissipation fin ( 4 ). The fin ( 4 ) is made of expanded metal sheet.

The present invention relates to a heat exchanger, and more particularlyto a mechanical heat exchanger.

A heat exchanger generally comprises tubes, through which a heattransfer fluid is intended to flow, and heat exchange elements connectedto these tubes.

A distinction is usually made between brazed heat exchangers andmechanical heat exchangers depending on the method for manufacturingthem.

In a mechanical heat exchanger, the heat exchange elements, referred toas “fins” in this case, are connected to the tubes in the following way.First of all, through-holes for the tubes to pass through are made inthe fins. These through-holes are generally each delimited by a raisededge forming a neck. Next, the fins are disposed substantially parallelto one another and each tube is inserted into a row of aligned holes inthe fins. Finally, a radial expansion of the tubes is brought about bypassing an expansion tool through the inside of these tubes so as tomechanically join the tubes and the fins by crimping, the necksdelimiting the through-holes for the tubes then forming collars clampedaround the tubes.

The fins of this type of tube are generally made from smooth metalsheets.

The aim of the invention is to propose a heat exchanger in which theheat exchange performance is improved while the mass thereof is limited.

To this end, the subject of the invention is a heat exchanger comprisingat least one tube for heat transfer fluid to flow through, connected toat least one heat dissipation fin, characterized in that the fin is madeof expanded metal sheet.

The fact that the fin is made of expanded metal sheet makes it possibleto increase the heat exchange between the air and the fin while limitingthe mass of the heat exchanger, since the heat exchange surface area ofthe fin is increased compared with a smooth metal sheet, withoutotherwise adding material thereto.

In one particular embodiment, corresponding to a mechanical heatexchanger, the tube is connected to the fin by clamping the tube in acollar formed in the fin.

Preferably, in order to further increase the heat exchange between theair and the fin, with the heat exchanger comprising a row ofsubstantially parallel tubes, the fin comprises at least one row ofdeflectors forming louvers, said row being formed in the fin andinterposed between two tubes of the row of tubes.

In one particular embodiment of the invention, the expanded metal sheetcomprises meshes that are each in the overall shape of a rhombus.

Preferably, in order to lighten the heat exchanger, the expanded metalof the sheet comprises aluminum.

The invention also relates to a method for manufacturing a fin of a heatexchanger according to the invention, the fin being formed from a metalsheet, characterized in that

-   -   a) the metal sheet is compressed between two complementary rows        of aligned teeth borne respectively by two jaws of a press;    -   b) the two rows of teeth are moved by half a pitch, a pitch        corresponding to the distance between the consecutive apices of        two teeth in the same row;    -   c) the metal sheet is moved transversely to the rows of teeth by        a distance corresponding to the width of one tooth;    -   d) step a) is repeated;    -   e) the two rows of teeth are moved by half a pitch in the        opposite sense to that in step b);    -   f) steps a) to e) are repeated;    -   g) through-holes for a tube to pass through are formed.

In one particular embodiment, the method includes the additional step offorming louvers between said through-holes.

The invention will be understood better from reading the followingdescription, which is given solely by way of example and with referenceto the drawings, in which:

FIG. 1 is a partial perspective view of a fin of a heat exchangeraccording to one particular embodiment of the invention;

FIGS. 2 to 7 are schematic perspective views of a press formanufacturing a fin during different steps in a method for manufacturingthe fin according to one particular embodiment of the invention.

FIG. 8 is a schematic view of a heat exchanger according to theinvention.

FIG. 1 shows a fin of a mechanical heat exchanger 1 intended to equip amotor vehicle.

The heat exchanger comprises a row of substantially parallel tubes 2through which a conventional heat transfer fluid is intended to flow,and superposed heat dissipation fins 4 that are connected to these tubes2.

The tubes 2 are connected to the fins 4 by clamping the tubes in collars6 formed in the fins 4. To this end, the fins 4 are provided withthrough-holes 8 for the tubes to pass through. These through-holes 8 areeach delimited by an edge forming a collar 6 and having two long edgeportions connected by two short semicircular edge portions. Thethrough-holes each have an oblong overall shape with long portions whichare slightly concave in their middle.

In the example described, the tubes 2 each have a shape corresponding tothat described by the through-holes. The tubes 2 are arrangedsubstantially parallel to one another, so as to form a single row.

The fins 4 have a substantially flat rectangular overall shape and arearranged in the heat exchanger 1 in a manner substantially parallel toone another and perpendicular to the longitudinal directions of thetubes 2.

The heat exchanger 1 allows an air flow to pass from upstream todownstream, the fins 4 being intended to extend through this flow.Arrows F indicate the direction of travel of the flow in FIG. 1.

In order to increase the heat exchange between the flow F and the fins4, the heat exchanger 1 also comprises rows 10 of deflectors 12 forminglouvers, which are formed in each fin 4 and are each interposed betweentwo tubes 2.

The fin 4 is made of expanded metal sheet, and consequently so are thedeflectors 10. Preferably, the metal of the sheet comprises aluminum,for example an alloy comprising substantially aluminum.

More particularly, the expanded metal sheet comprises meshes 12 that areeach in the shape of a rhombus.

A method for manufacturing a fin 4 of a heat exchanger 1 according tothe invention will now be described, the steps of said method beingillustrated in FIGS. 2 to 7.

Since the fin 4 is formed from a metal sheet 16, this metal sheet 16 isfirstly compressed between two complementary rows 18 of aligned teeth 20that are borne respectively by two jaws 22 of a press 24.

This is realized for example by lowering the upper jaw 22 in thedirection and sense indicated by the arrow C in FIG. 2, the compressionbeing illustrated in FIG. 3.

Next, the two rows 18 of teeth are moved by half a pitch, a pitchcorresponding to the distance p between the consecutive apices of twoteeth 20 in the same row 18. This movement is indicated by the arrow P₁in FIG. 4.

Then, the metal sheet 16 is moved transversely to the rows 18 of teethby a distance d corresponding to the width of one tooth 20. Thismovement is indicated by the arrow D shown in FIG. 5.

Once the step of compression between the rows 18 of teeth 20 has beenrepeated, as shown in FIGS. 5 and 6, the two rows 18 of teeth 20 aremoved by half a pitch in the opposite sense to the arrow P₁, that is tosay in the sense of the arrow P₂, shown in FIG. 7.

In order to obtain the expanded metal fin 4 as shown in FIG. 1, theabove steps are repeated until the entire surface of the sheet 16 hasbeen compressed, and then the holes and the louvers are realized.

The invention is not limited to the embodiment presented, and furtherembodiments will be dearly apparent to a person skilled in the art. Forexample, according to an embodiment that is not shown, the tubes have acircular cross section and the corresponding through-holes are circular.

1. A heat exchanger comprising: at least one tube for heat transferfluid to flow through, connected to at least one heat dissipation fin,wherein the fin is made of expanded metal sheet.
 2. The heat exchangeras claimed in claim 1, the tube being connected to the fin by clampingthe tube in a collar formed in the fin.
 3. The heat exchanger as claimedin claim 1, further comprising a row of substantially parallel tubes,wherein the fin comprises at least one row of deflectors forminglouvers, said row being formed in the fin and interposed between twotubes of the row of tubes.
 4. The heat exchanger as claimed in claim 1,wherein the expanded metal sheet comprises meshes that are each in theoverall shape of a rhombus.
 5. The heat exchanger as claimed in claim 1,wherein the expanded metal sheet comprises aluminum.
 6. A method formanufacturing a fin of a heat exchanger as claimed in claim 1, the finbeing formed from a metal sheet, the method comprising: a) compressingthe metal sheet between two complementary rows of aligned teeth bornerespectively by two jaws of a press; b) moving the two rows of teeth byhalf a pitch, the pitch corresponding to the distance between theconsecutive apices of two teeth in the same row; c) moving the metalsheet transversely to the rows of teeth by a distance corresponding tothe width of one tooth; d) re-compressing the metal sheet between thetwo complementary rows of aligned teeth e) moving the two rows of teethare moved by half a pitch in the opposite sense to that in step b); f)repeating steps a) to e); and g) forming through-holes for a tube topass through.
 7. The method as claimed in claim 6, further comprisingthe additional step of forming louvers between said through-holes.